Enable ignoreOrder option for extract-text-webpack-plugin

[sebilasse]

Bug

The bug is described pretty well in
webpack-contrib/extract-text-webpack-plugin#386

Package Version: latest

Actual behavior:
dojo build -m dev -w memory -s
After updating about the half of my widgets the bug described above happened,
and unfortunately it is not possible to debug the reason because the only message is
Order in extracted chunk undefined

See also "Interestingly, it's not deterministic." ff.
webpack-contrib/extract-text-webpack-plugin#80 (comment) (same here)

There is an ignoreOrder flag documented here
https://github.com/webpack-contrib/extract-text-webpack-plugin#options

[sebilasse]

it is caused by base.config.js in https://github.com/dojo/cli-build-app -
will do a PR there